A set of interactive computer programs for three dimensional reconstruction and display of asymmetric biomolecules from electron micrographs was written and tested on chick ribosome dimers. These programs can be applied to any set of tilted micrographs. Fortran subroutines were written for an inexpensive, accurate halftone display of images on graphics storage tube computer terminals. A reconstruction algorithm was devised which used all the available information on the spatial localization of every detected photon. This algorithm makes maximal use of gamma rays in 3D nuclear medicine. It is also applicable to single-count electron microscopy, and thus may contribute to solving the beam damage problem. Most enzymes have not been crystallized, and thus their structure cannot be determined by x-ray or neutron crystallography. The mathematics and computer programs being developed will permit us to reconstruct the 3D structure of individual, asymmetric macromolecules at moderate resolutions.